Nengpan Ju

A Real-time Monitoring and Early Warning System for Landslides in Southwest China

Landslides not only cause property losses, but also kill and injure large numbers of people every year in the mountainous areas. These losses and casualties may be avoided to some extent by early warning systems for landslides. In this paper, a realtime monitoring network and a computer-aided automatic early warning system (EWS) are presented with details of their design and an example of application in the Longjingwan landslide, Kaiyang County, Guizhou Province. Then, according to principle simple method of landslide prediction, the setting of alarm levels and the design of appropriate counter-measures are presented. A four-level early warning system (Zero, Outlook, Attention and Warning) has been adopted, and the velocity threshold was selected as the main warning threshold for the landslide occurrence, but expert judgment is included in the EWS to avoid false alarms. A case study shows the applicability and reliability for landslide risk management, and recommendations are presented for other similar projects.

Assessment model for earthquake-triggered landslides based on quantification theory I: case study of Jushui River basin in Sichuan, China

Earthquakes that occur in a mountainous region can trigger a mass of landslides (ETL), and these hazards can cause relatively heavy casualties. Compared with other evaluation models and methods, quantification theory I is a multivariate statistical approach that can simultaneously process qualitative and quantitative variables. On the basis of the ETL features and the influencing factors, in this paper, we select lithology, slope gradient, slope height, slope structure, distance to seismogenic fault, hanging wall/footwall of the seismogenic fault, and rock integrity, a total of seven impact factors, as the assessment index. By randomly selecting 128 single slopes in an intense seismic area as the samples, we develop an assessment model and apply it to investigate the regional stability of the Jushui River basin to prove its applicability. Moreover, this method calculates the factor weight; this can also prove the method through a comparison with the existing research results obtained using other methods.

Effectiveness of Fiber Bragg Grating monitoring in the centrifugal model test of soil slope under rainfall conditions

Centrifugal model tests are playing an increasingly important role in investigating slope characteristics under rainfall conditions. However, conventional electronic transducers usually fail during centrifugal model tests because of the impacts of limited test space, high centrifugal force, and presence of water, with the result that limited valid data is obtained. In this study, Fiber Bragg Grating (FBG) sensing technology is employed in the design and development of displacement gauge, an anchor force gauge and an anti-slide pile moment gauge for use on centrifugal model slopes with and without a retaining structure. The two model slopes were installed and monitored at a centrifugal acceleration of 100 g. The test results show that the sensors developed succeed in capturing the deformation and retaining structure mechanical response of the model slopes during and after rainfall. The deformation curve for the slope without retaining structure shows a steep response that turns gradual for the slope with retaining structure. Importantly, for the slope with the retaining structure, results suggest that more attention be paid to increase of anchor force and anti-slide pile moment during rainfall. This study verifies the effectiveness of FBG sensing technology in centrifuge research and presents a new and innovative method for slope model testing under rainfall conditions.

Statistical Analysis of the Key Factors of Landslide Induced by Wenchuan Earthquake

The distribution of landslides triggered by Wenchuan Earthquake is controlled by a variety of geological factors. Statistical results of 2,445 landslides of the four river basins show that all these factors, including the causative faults, slide direction, landform and the own properties of the slope have its contribution to the landslides distribution. In order to find out which factors have more significant influence on the landslide distribution, it is necessary to put all factors into consideration. Multivariate statistical analysis of these landslides shows that, in the near field of the causative fault during high intensity earthquake, landslides were affected distinctly by the strength of the seismic wave, instead of the properties of the slope itself such as slope structures and lithology. The factors can be generalized into five parts, which represent 76.15 % of the data set. In these factors, the first three are directly connected to the strength of the seismic wave, and the last two components involving the nature of the slope itself. Both the field investigation and statistic reveal that in the strong shock mountainous areas, the structure of the slope is not so important as usual.

Designing an Android-Based Application for Geohazard Reduction Using Citizen-Based Crowdsourcing Data

Application development based on mobile platform is regarded as one of the major trends in information communication technology. However, only a few cases of mobile application are available for geohazard reduction using citizen-based crowdsourcing data. With the development of geohazard informatization and the rapid progress of mobile technology, the design and implementation of phone-based applications that could be used to monitor and prevent geohazards have been received increasing attention. Aiming at minimizing the threat of geohazards to people’s lives and assets, this paper presents an android-based application named Geohazards Group Measurement and Guards against System (GGMGAS). Local villagers use the GGMGAS to collect field data, including photos and videos, and transmit them to a database server. Therefore, the efficiency and stability of the data exchange between the mobile phone and the database server is very important. A design method and system solution of a data-exchange scheme was designed based on the WebService technology. Through trial operation, it has been found out that this data-exchange scheme could greatly improve the communication efficiency and the stability of collected field data. Practice has proved that this method based on citizens’ crowdsourcing data can effectively reduce the losses caused by geohazards.

Route Alignment and Optimization of Railway Based on Geological Condition

Characterized by high seismic intensity and high geological disaster risk, the geological condition of Longmenshan is complex and unique. How to carry out route alignment in such complicated geological background and avoid geohazards is one of key issues. Based on the geological background, including landform, lithology, Geological tectonic, geohazards distribution, acquired by remote sensing and field investigation, this paper firstly compared route schemes of the Chengdu-Lanzhou railway in Longmenshan mountain area, and regarded the Jushui river basin as recommendation for relatively less geohazards and no gobs. Then this paper secondly evaluated route schemes related to geohazards distribution and geohazards features in Jushui river basin, and regarded the D2K scheme as preferred option, which avoid large-scale and typical geohazards in the form of “early into tunnel and later out of tunnels” by longer tunnels.

Information Management System of Landslides Triggered by Wenchuan Earthquake on 12th May, 2008: --Based on WebGIS and Database Technology

Wenchuan Earthquake triggered more than thousands of landslides, which seriously threatened the lives and properties of local people in the disaster areas. Even though emergency investigation and monitoring have been carried on after the earthquake in order to make sure the reconstruction work well, there is still need an effective way to manage the considerable disaster information immediately. This paper presents a preliminary study of a WebGIS-based approach to the representation, organization and access of geohazard information-including map & data query, statistic, spatial analysis and early warning. The system is not only to assist in the decision-making process for administrator to prevention disaster, but also to provide a platform for the more end-users with limited GIS knowledge to understand the geohazard and a cost-saving solution to access up-to-date spatial datasets customized for a specific topic.

Application Development in Classification of Rock Mass Quality on Tunnel Engineering

Classification of rock mass quality is the basis of stability assessment, which plays a very important role on tunnel engineering. Especially, the construction of railways, with a series of new characteristic such as “Long, Large and Deep”, has progressed at great speed and has gradually extended to mountainous areas at the background of western development strategy. No matter whether in investigation, design and construction, classification of rock mass quality costs much time and effort. Based on summary and analysis of a variety of classification methods, this paper establishes a general index system and criteria of zone division on tunnel surrounding rock and develops a user-friendly, convenient program which can make zone division of surrounding rock and classification of rock mass quality become easily and diagram exported interactively. The case study shows that the results are in a good agreement with the actual situation. The proposed method should be more feasible for future tunnel construction and for suggestions of tunnel support design in the mountain areas of China.